Two studies examined the choice differences between prosocials and proselfs by examining the influence of norms of social responsibility and reciprocity. In line with the integrative model of social value orientation, it was expected that prosocials differ from proselfs in their level of cooperation because they wish to maximize own and other's outcomes (i.e. paralleling the norm of social responsibility) and enhance equality in outcomes (i.e. paralleling the norm of reciprocity). Study 1 revealed that prosocials felt more responsible to further the group's interest than proselfs did and this social responsibility feeling appeared to account for choice differences. Study 2 revealed that prosocials were more likely to reciprocate their partner's actions than were proselfs. Also, feelings of social responsibility did not account for this observation, suggesting that enhancing joint outcomes and equality in outcomes constitute two relatively independent dimensions. The findings are discussed in light of the integrative model of social value orientation. Copyright © 2001 John Wiley & Sons, Ltd.